Comparative study of Mo and W Bonding Layers on Graphite during Plasma Spraying

Title: Protective coating on Carbon at elevated temperature Abstract Carbon substrate is useful at high temperature application in many engineering field such as heat-treating, brazing, sintering industries. As the process temperature becomes severer and severer, carbon substrate experiences degradation leading to failure. Protective coatings of ceramic is essential on carbons substrate by air plasma spraying. To enhance the bonding between carbon substrate and ceramic top coating, an intermediate layer with W and Mo is applied and its behavior was investigated and compared in view point of bonding force. W was found inferior to Mo as bonding layer in view of carbide formation over 1450¡É against thermodynamic data. The phenomena was related with formation of a new barrier layer during air plasma spraying. X-ray and scanning microscope were used to observe the cross-section of coatings between susbstrate and top layer. The different bonding characteristic between W and Mo was analyzed by identifying a new phase formation.